Corrosion inhibition with nitrobenzaldehydes



Patented Dec. 15, 1953 signoi'. to Shell Development. Company, San Francisco, Calif., a corporation. of Delaware.

No Drawing. Application May 2, 1949", Serial No. 91,019

9f Claims.

This invention relates to the prevention of 601"- rosion of metal surfaces, and especially toithe; inhioition of corrosion of metals which are normally corrodilole in the presence of Water vapor; and air, or aqueous condensates and air. More particularly, the present invention pertains to novel compositions for, and novel methods of, inhibiting corrosion of. such metals, that is. oxidative corrosion. In one of its. specific. emhodiments, this invention relates to metal articles packaged according to. the teachings herein.

musing. storage, handling; transportation, operation,.and distribution of objects having. metalliierous, particularly ierruginous, surfaces, such as. tools, machines, moving metal parts, machined surfaces, sheets of metal, steel cans, tanks, metal containers, shell-cases, fire-arms, bulletv cases, rocket-heads, metal tubes, pipes, and conduitenclosutes, it is often necessary to prevent corrosion caused by water vapor contacting such. metal surfaces, Metal articles, or articles having' metallic surfaces, which are unprotectedirom corrosion. or only partly protected by inadequate means, such as a partially pervious coating, often require suitable inhibitors which prevent metal corrosion in the presence of water vapor, liquid eater, or aqueous condensates which may contain. compounds or salts which ordinarily pro.- mote such corrosion.

Partially enclosed or metal-containing objects are usually housed, packaged, enveloped or placed ina container unde-r such conditions that moisture is either pres cut at the outset or may enter through. the container walls, thereby causing corrosion. For ex ample, although various machined parts are usually packaged in waxed or oiled paper or in other materials which in fact are only partially ixn permeable to water vapor, it has been found necessary also to. coat the metal surfaces with a protective coating of, for example, oil, grease, or the like, in order to obtain a further degree of. corrosion prevention. In many cases additional corrosion preventive means have been resorted to, e. g., the. use within the container or package of a dehydrating agent of the type of. silica. gel or alumina. Even when the container Walls are absolutely impervious to. gases or Water vapor, corrosion of the metal parts will still occur hecause it is substantially impossible to avoid entry of water vapor at the time when said parts are losing placed in a. container.

Consequently, it. is: an object of this invention to provide novel methods and means for inhibiting corrosion of metals normally corrodi-ble in: the presence of- Water vapor and air or oxygen. It is another object of the. present invention to provide volatile corrosion inhibitors suitable. for preventing corrosion of such metals disposed in enclosed spaces. A further object is to provide completely enclosed as. vapor phase. corrosion inhibitors.

2. volatile corrosion inhibitors. and methods of app ying such, whereby an atmosphere containing the. corrosion inhibitor vapors will effectively in hihit corrosion of metal surfaces in contact with said atmosphere, even. in the. presence. of Water vapor and air, Another oloiect of this invention is. toprovide. novel corrosion-inhibiting packagingmaterials for use. during storage, shipping, etc, of metallic objects. A still further object is. to provide packaged metallic articles, particularly articles made of ironand its alloys, which are. protected against. corrosion by water vapor and air. Additional objects will become apparent hereinafter.

It has now been discovered that. the above and other objects may be attained bymaintaining in contact with surfaces of metals normally corrodible by water vapor and oxygen, vapors of a nitrobenzaldehyde or ring substituted lower alkyl derivatives thereof. Preferred compounds. for use according to this invention are the three isomeric unsubstituted mono-nitrobenzaldehydes, meta-nitro.benzaldehyde being considered to. give the cost results.

The term a nititobenzaldehyde is. intended to include only thethxee isomers, ortho-, meta, and para-nitrobenzaldehyde. Ten term lower alkyl. derivatives thereof is; intended to. include only the. above. isomeric. nitrobenzaldehydes having lower alkyl groups attached: to the benzene ring. By lower alkyl is meant hydrocarbon radicals, preferably saturated, having not more than about 3 carbon atoms. If more than one alkyl radical is present, the total number of carbon atoms in all such radicals preferably not, more than about 4... Suitable examples of such. compounds are Z-nitrwS-ethyl benzaldehyde, 2-nitro=3- etlivl-a-methyl ben-zaldehyde, tetramethyl-mnitrobenzaldehyde, 5-isopropy1-3-nitrobenza1dehyde, 5-methyl-S-nitrobenzaldehyde and l-nitro- E-meth-yl-m-toluic aldehyde.

As stated above, the metals which are sitestively protected according to this invention are those which. are normally corroded in the pres once of Water vapor and air or. oxygen. Included in. such are the. various ferrous metals such as Armco iron,'plain carbon steels of low, medium and high carbon. content, cast irons, and alloy steels, including high alloy content steels, ferritic and austemtlc steels, and the like. Also protected by the inhibitors of. this invention are various non-ferrous metals such as copper, aluminum, magnesium, etc, and the non-ferrous alloys of such. Protection may also be achieved for con ples of dissimilar-metals, such as couples of steels with copper, aluminum, nickel, chromium, and alloys of these metals.

Various techniques are effective in the utilization oi the present nitrobenzaldehyde compounds Within any enclosing means or container, corrosion of metal surfaces by moisture is prevented by the presence, in. the enclosed atmosphere, of very small amounts of the above compounds. These compounds may be originally introduced into the enclosure as a solid, liquid, or vapor, in a solution, or as an emulsion or a dispersion, etc., just so long as the inhibitor may vaporize and diffuse throughout the atmosphere in contact with the metal within the enclosures. Thus, a metal article may be enclosed in a container together with inhibitors as crystals or as a power; or there may be introduced into the enclosure or container a piece of solid, preferably an. absorbent or fibrous material, coated or impregnated with the present nltrobenzaldehyde compounds.

In a preferred embodiment of the instant invention the present vapor phase inhibitors are coated upon, or impregnated within, a solid sheet packaging or wrapping material, such as paper, cardboard, cloth or various textile materials, metal foil, plastic films or sheets, and the like, which be used for wrapping metallic objects. Laminates of the above materials, only parts of which are impregnated with, or otherwise contain, the above inhibitors, are also useful. In the case of the latter type of packaging material, the metal is preferably wrapped so that the inhibitor-containing side of the Wrapping is toward the metal. The nitrobenzaldehyde may be impregnated in the wrappings by various means, such as, e. g., dissolving them (the inhibitors) in a relatively volatile solvent therefor, such as acetone, soaking the wrapping in the re-- sulting solution and allowing the solvent to evaporate. The inhibitors may also be coated on the various materials, such as by means of a suspension in an adhesive starch or the like.

After providing the containers with the inhibitors in any of the above or equivalent forms, the containers may then be closed or sealed. The resultant container or package need not be completely air tight, but only has to be closed to the extent that a corrosion-inhibiting concentration of vapors is retained or maintained within the package.

In cases wherein free circulation of air is prevented around metal articles in storage, the inhibitor(s) is also effectively utilized by introducing it as a vapor, or by providing an atmosphere containing vapors of the nitrobenzaldehyde around the metal articles. Corrosion by circulation of air over metal surfaces can be prevented by partially or substantially saturating the introduced air with vapors of the inhibitor(s). Metal parts can be efiectively corrosion-proofed by coating them with the inhibitor(s) by depositing the latter from a solution or a dispersion, or from heated vapors contacting a cooler metal, or by incorporating the inhibitor(s) in relatively non-volatile coating materials which remain on the metal.

The metal walls or parts enclosed within pipes, machin ry, or instruments are prevented from corroding either by enclosing the inhibitor(s), or by otherwise making the inhibitor available, within the vapor spaces present therein, e. g., in hydraulically operated mechanisms. In a preferred method the inhibitor(s is disposed in and allowed to vaporize from the hydraulic fluid utilized in such mechanisms. When disposed in a liquid, the nitrobenzaldehydes of this invention not only inhibit corrosion of metals contacted by this liquid but also inhibit corrosion of metals 4 contacted by the vapors in the vapor phase above the liquid.

Corrosion of metal surfaces which define combustion zones and/or other internal regions of engines, e. g., of internal combustion or steam engines, may be prevented by connecting inlets thereto with sources capable of supplying the inhibitor(s).

Aerosols are also effective for distributing the inhibitor(s) In such a case, the inhibitor is dissolved in a liquefied, normally gaseous solvent which is under sufficient pressure in a vessel to maintain the solvent in its liquid state. The solution of the inhibitor thus prepared is released through a restricted orifice in th vessel, thereby distributing the inhibitor in a state of minute subdivision.

The present inhibitors are efiective agents for reducing corrosive wear of moving machined metal parts, particularly in engines, e. g., steam engines, steam turbines, internal combustion engines, etc. The inhibitors are incorporated into the fuel or lubricant for such engines or machinery and thereby the wear attendant upon corrosion is inhibited.

A particularly advantageous characteristic of the invention is that under ordinary atmospheric conditions of temperature and pressure the present inhibitors are solids having vapor pressures of only a fraction of a millimeter of mercury, and the concentration of these materials in the vapor phase is limited thereby; any additional inhibitor is present in the condensed phase and acts as a reservoir to replace inhibitor vapors which escape from the package, are used up, or are other Wise removed from the corrosion-inhibiting atmosphere. An additional advantage of the present type of corrosion inhibitor is readily seen to be that whereas corrosion rates increase with increasing temperatures, so do the vapor pressures (and consequently the vapor concentrations) of the corrosion inhibitors. Therefore, additional protection is automatically provided when needed.

From the above, it is obvious that the duration, but not the degree, of corrosion protection is dependent upon the amounts of nitrobenzaldehyde compounds used in accordance with this invention, with the obvious reservation that the initial supply must be sufiicient to build up a corrosion inhibiting concentration. Since the vapor pressures of the inhibitors are so small, very minute amounts of inhibitor will satisfy thi latter requirement. Consequently, the amount to be used in any particular application will depend upon such things as the length of time for which protection is required and upon the rate at which the inhibitor is allowed to escape, and will vary with the individual applications. In general. satisfactory results are attained when the in hibitor is present in an amount of between about 0.01 gm. and about 15 gm. (for average conditions about 1 to 4 gm.) per cubic foot of enclosed vapor space. In the case of wrapping, or packaging materials, between about 0.01 gm. and about 5 gm. of inhibitor per square foot of sheet material is generally satisfactory. It should be obvious, however, that extreme conditions may require much greater or much smaller amounts than those stated.

Although not necessary for the complete understanding and successful practice of this invention, the following examples are presented to show the surprising results which may be attained by the use of the present vapor phase corrosion inhibitors. It is emphasized that these examples are merely illustrative, and the invention should in no way be construed as limited thereby.

EXAMPLE A One-half gram of m-nitrobenzaldehyde was placed in the bottom of a 125 ml. reagent bottle. The bottle was closed with a stopper having a single hole through which a 4 inch length of mild steel rod was inserted in such a manner that one end of the rod was exposed to the atmosphere within the bottle and the other end was exposed to the atmosphere outside of the bottle. The bottle was partially immersed in a controlled-temperature bath at 130 F. for 1 day. At the end of this time the temperature differential between the bottom of the bottle (immersed in the bath) and the steel rod (one end exposed to room temperature) had resulted in the deposition of crystals of m-nitrobenzaldehyde upon the relatively cool steel surface.

One-half cubic centimeter of H20 was then put into the bottle, and the bottle (with stopper and steel rod in place) was exposed to three 24-hour cycles, each of which consisted of 6 hours at 90 F. 1 hour passing from 90 F. to 60 F. 11 hours at 60 F. 6 hours passing from 60 F. to 90 F.

Only about of the surface of the steel rod which was exposed to the m-nitrobenzaldehyde contained a very light rust whereas a steel rod given an identical treatment but without the presence of m-nitrobenzaldehyde had nearly 100% of the surface covered with rust.

EXAMPLE B A piece of 30 pound kraft paper was treated with an acetone solution of m-nitrobenzaldehyde and the acetone evaporated, leaving the paper impregnated with nitrobenzaldehyde in the amount of 1 gm./sq. ft. of paper. This paper and a strip of mild steel were placed under a bell jar for 14 days, over water, at 40 C. in air with a relative humidity of 92% to 100%. Both air and water were continuously replaced. The metal was completely exposed to the humid atmosphere and was not in contact with the paper. As a control, a similar piece of steel was exposed to the same conditions with the single exception that the kraft paper was not impregnated with the nitrobenzaldehyde. The metal strip in the bell jar with the impregnated paper was completely free of rust, whereas over 60% of the surface of the control was covered with rust.

EXAMPLE 0 Polished inch by 2 inch strips of boiler plate steel were suspended over 0.1 gm. each of various compounds plus 0.1 gm. distilled water in 125 milliliter glass-stoppered bottles for '7 days. The final appearances and changes in weight of the metal strips are listed in Table I.

I claim as my invention: 1. A substantially solid sheet packaging material containing a compound selected from the group consisting of isomeric nitrobenzaldehydes and the lower alkyl derivatives thereof in an amount of between about 0.01 gram and about 5 grams per square foot of said substantially solid sheet packaging material.

2. In a method for inhibiting corrosion of a metal surface normally corrodible by contact with water vapor and air, the step of maintaining in an atmosphere contacting said surface an effective vapor-phase corrosion-inhibiting concentration of o-nitrobenzaldehyde.

3. A substantially solid sheet packaging material having associated therewith m-nitrobenzaldehyde in an amount of between about 0.01 gram and about 5 grams per square foot of said substantially solid sheet packaging material.

4. A substantially solid sheet packaging material having associated therewith an unsubstituted nitrobenzaldehyde in an amount of between about 0.01 gram and about 5 grams per square foot of said substantially solid sheet packaging material.

5. A substantially solid sheet packaging material containing an effective corrosion-inhibiting amount of a lower alkyl substituted nitrobenzaldehyde in an amount of between about 0.01 gram and 5 grams per square foot of said substantially solid sheet packaging material.

6. A packaging material comprising paper having associated therewith m-nitrobenzaldehyde in an amount of about 1 gram per square foot of said paper.

7. In a method for inhibiting corrosion of a metal surface normally corrodible by contact with water vapor and air, the step of maintaining in an atmosphere contacting said surface an eiTective vapor phase corrosion inhibiting concentration of a compound selected from the group consisting of isomeric nitrobenzaldehydes and lower alkyl derivatives thereof.

8. A substantially solid sheet packaging material having associated therewith ortho-nitrobenzaldehyde in an amount of between about 0.01 gram and. about 5 grams per square foot of said substantially solid sheet packaging material.

9. The combination comprising a metal article normally corrodible by contact with water vapor and oxygen and a substantially solid covering material enclosing said metal article, said covering material containing a corrosion inhibitor of the group consisting of nitrobenzaldehydes and lower alkyl derivatives thereof, said inhibitor being present in an amount sufficient to maintain a corrosion inhibiting atmosphere about the enclosed metal article.

WILFRID W. NEWSCI-IWANDER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,151,255 Ferguson Aug. 24, 1915 1,185,361 Albu May 30, 1916 1,613,808 Schreiber Jan. 11, 1927 2,064,325 Sutton et al. Dec. 16, 1936 2,155,731 Mitchell Apr. 25, 1939 2,185,238 Whaley Jan. 2, 1940 2,194,370 Walker Mar. 19, 1940 2,253,655 Shurley Aug. 26, 1941 2,512,949 Lieber June 2'7, 1950 FOREIGN PATENTS Number Country Date 596,160 Great Britain Dec. 30, 194? 620,056 Great Britain Jan. 18, 1948 

1. A SUBSTANTIALLY SOLID SHEET PACKAGING MATERIAL CONTAINING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ISOMERIC NITROBENZALDEHYDES AND THE LOWER ALKYL DERIVATIVES THEREOF IN AN AMOUNT OF BETWEEN ABOUT 0.01 GRAM AND ABOUT 5 GRAMS PER SQUARE FOOT OF SAID SUBSTANTIALLY SOLID SHEET PACKAGING MATERIAL. 